The present invention relates to a low-cost damping system which improves bicycle suspension performance, and more particularly, controls damping of a bicycle suspension system during both compression and extension of the system.
Suspension systems are used for various applications, such as for cushioning impacts, vibrations, or other disturbances experienced in the operation of vehicles and machinery. Typical applications, for example, include cushioning impacts experienced by bicycles and motorcycles. For example, bicycles have been developed with suspension systems for cushioning impacts or vibrations experienced by the rider when the bicycle contacts bumps, ruts, rocks, pot holes, or other obstacles. Typically, such bicycle suspension systems have been configured for use in the front or rear bicycle fork, in the head tube that connects the front fork to the bicycle frame and handlebars, in the seat post, and in conjunction with a rear wheel swing-arm assembly, as well as in other locations.
Bicycle suspension systems typically include a pair of telescoping elements or tubes which are biased apart by one or more biasing elements, such as coil springs, air springs or elastomer members. The energy generated by an impact to the bicycle is typically stored temporarily by the biasing elements, which are compressed during the impact. These biasing elements may alternatively be arranged within the suspension system to be stretched during impact. However, for purposes of simplicity of the description herein, the biasing elements are hereinafter referred to as "compression members" which are compressed during impact. Much of this stored energy, however, is immediately returned to the system during an expansion of the system in what is known as the "rebound" of the system, during which the compressed or stretched members return to their original size, causing the bicycle to recoil upward and/or downward. Thus, there exists a need to provide damping to control the compression and expansion of the suspension system.
Damping systems, such as hydraulic shock absorbers, are well known in the motorcycle and automobile fields. Damping systems for bicycle suspension systems are also known, such as described in U.S. Pat. No. 5,456,480 to Turner et al., which patent has been assigned to the assignee of the present invention, and is incorporated herein by reference herein in its entirety. Turner specifically discloses a hydraulically damped shock absorber for use in a bicycle fork. Although such systems provide favorable damping characteristics, they can be sophisticated and complicated and thus costly to manufacture. Additionally, although improvements have been made to hydraulic damping systems in order to reduce their weight, and particularly to reduce the weight added by the damping fluid, it would be desirable to provide a still lighter weight system. In particular, it would be desirable to provide a damping system that does not require damping fluid at all. The elimination of damping fluid is also desirable to eliminate the potential for fluid leakage from a damping system utilizing damping fluid. There continues to exist a need for simple, inexpensive and lightweight damping systems suitable for use in bicycle suspension systems.